This proposal is in response to a program announcement for a pilot grant (PAR-98-021) and the category is number 3: Cartilage aging/Osteoarthritis (OA). This is a pilot study to develop new clinical diagnostic tools for OA (improved methods to quantitate data from MRI scans). The investigator is an established investigator, however, with no funding in the area of OA. This is a new area of research for the PI which uses previously developed infrastructure, resources and experience in MR imaging to develop new MR tools for comprehensively characterizing the entire joint in OA. This grant represents the PIs concerted effort to diversify and develop a comprehensive program that addresses the issue of the aging musculo-skeletal system. Using the data in this grant as preliminary data the PI will be in a position to potentially develop a R01 and establish a new exciting role for MR in OA. OA is a disease of articular cartilage degeneration, however, in the pathogenesis of OA, interactions between all the major joint tissues, including the articular cartilage, synovium, subchondral and trabecular bone and muscle have been implicated. The disease is characterized by a long asymptomatic phase when articular cartilage degenerates and radiographic changes develop and a symptomatic or painful stage that develops after irreversible cartilage damage has occurred and radiographic changes progress. It has been hypothesized that articular degeneration and progression of OA may be preceeded by changes in subchondral and trabecular bone. Although trabecular bone interactions are implicated in early OA, the changes in the trabecular bone adjoining the articular cartilage, associated with OA are unclear and the trend of changes has not been defined conclusively. In radiographic projection images the presence of osteophytes complicates the evaluation of the subchondral plate and adjoining trabecular bone, and micro computed tomography examinations are in vitro. In this context magnetic resonance imaging (MR), which has recently been used to depict trabecular bone structure may potentially be a valuable tool, particularly since MR images may also be used to quantify the cartilage morphology, volume and thickness. In this application, we are proposing to make use of recent advances in MR hardware and software, to accurately quantify (i) the 3-D architecture of the trabecular bone network adjoining the articular cartilage, (ii) establish its' reproducibility, and (iii) variations in normal and osteo- arthritic (mild and severe or Kellgren-Lawrence scale 1 and 4) subjects, and (iv) combine these measures with MR based measures of cartilage thickness and volume and relate them to clinical measures such as pain and disability (WOMAC scale, Health Activity Questionnaire, etc.).